The present invention relates to a process for manufacturing small combustible bricks from plant materials and in particular to a process which does not employ binders.
The manufacture of combustible bricks by agglomeration, without an additional binder, of waste products of plant origin is already known. Various waste products have been employed for this, such as wood scrap, wood shavings, wood sawdust, shells of fruit or grains or plant fractions of industrial or town waste products.
By a continuous or discontinuous process, a press agglomerates these waste products so as to make small combustible bricks of various shapes and sizes therefrom.
Before being introduced into the press the waste products are directly and successively subjected to two treatments for their prior conditioning:
MECHANICAL PULVERIZATION TREATMENT FOR OBTAINING THE NECESSARY PARTICLE SIZE (BY MEANS OF SHREDDERS, CRUSHERS, GRINDERS, ETC);
AND A DRYING HEAT TREATMENT FOR BRINGING THEIR MOISTURE CONTENT TO GENERALLY LESS THAN 15% (BY MEANS OF DRIERS WITH HEAT GENERATORS OF VARIOUS TYPES).
However, and in particular with the cheaper continuous process, this manufacture without an additional binder gives rise to difficulties and defects:
A. The diversity of the origins of the waste products results, in the course of manufacture, in large variations in the characteristics of the material received by the press.
B. The extraction of moisture contained in the waste products requires for the drying relatively high temperatures, which may be as high as 400.degree. C and these are harmful to the correct operation of the press and might result in localized carbonization with subsequent risk of spontaneous combustion of the bricks.
C. A moisture content of at least 10-11% is required for the agglomeration without a binder, which results in a reduction in the heating power/kilogram of the bricks, difficulties as concerns a correct combustion and a high content of steam in the smoke (resulting in condensations in the smoke flues and difficulties of utilization in respect of smoke curing houses and driers).
D. The bricks lack cohesion and uniformity in their structure and this renders them liable to break and deteriorate when being handled.